The proposed research effort is comprised of two interrelated parts: 1. An intensive analysis of interrelationships of reported smoking behavior, lung function and symptomatology, and other characteristics of some 15,000 persons participating in an ongoing, prospective population study of chronic obstructive respiratory disease (CORD) in four areas in Los Angeles County. As part of this analysis, changes in lung function, respiratory symptoms and smoking behavior over a five-year interval will be examined. The objectives of this analysis are: a) to determine whether there are particular sets of characteristics which permit identification of cigarette smokers who are at particularly high risk of developing disabling chronic obstructive pulmonary disease if they continue to smoke; b) to ascertain whether there are factors which discriminate between individuals who quit smoking and those who do not; c) to evaluate the influence of smoking cessation on respiratory symptoms and lung function; and d) to examine whether active smoking by one or more household members has an influence on respiratory symptoms and/or lung function of children and other household members who do not smoke (passive smoking). 2. A field intervention trial to be conducted among approximately 420 adult cigarette smokers undergoing screening for respiratory fitness as part of the existing CORD population study to determine whether smokers receiving an adverse health report regarding the presence and severity of lung function abnormalities will more likely quit smoking: a) if the health status communication is presented in an appropriately personalized and impactful manner, and b) if it is accompanied by detailed and specific recommendations regarding smoking cessation. Prior to the intervention trial, pilot work will be carried out in a comparable sample of 100 adult smokers to develop and evaluate the format and content of the health status communication and the specific recommendations to quit smoking. Outcome measures will include reported changes in smoking behavior verified by objectively determined end-expired carbon monoxide and salivary thiocyanate determinations.